Can the Ketogenic Diet Cause Muscle Loss?

Keto and Muscle Loss: Have you ever noticed that if you ask ten people about their experience with a popular diet, each person will give you a different answer? Some will call it a miracle, others will say they didn’t notice a difference, and others may even say they felt worse.

Different outcomes can happen with every diet – even the ketogenic diet. It shouldn’t be a surprise that we all respond differently. We have different genetics and lifestyles and come from different environments. So while the keto diet has impressive health benefits, we can’t ignore our biological individuality.

When following the keto diet long-term, some people report muscle gains and improvements in exercise. Still, a group of individuals experiences the opposite – muscle loss and increases in belly fat. This negative adaptation doesn’t happen to everyone, but knowing that this can happen is essential. Instead, we can design a lifestyle program that uses the body’s innate biology to make low-carb diets work without the downfall of muscle loss. First, we need to understand the science behind why this adaptation happens – and it starts with something called gluconeogenesis.

Keto and Muscle Loss: What is Gluconeogenesis?

To better understand why some people lose muscle while following keto, let’s start by examining the process of gluconeogenesis. Gluconeogenesis is a biological process that acts as a survival mechanism to keep energy stable in the body. During this process, glucose is created from non-carbohydrate sources in the liver and kidneys. If the body is low on energy reserves, gluconeogenesis can ramp up to provide glucose for a quick release. Alternatively, when there is plenty of energy available, the process of gluconeogenesis is inhibited.

You can think of gluconeogenesis as a catabolic process, breaking down protein and fat to make energy. It’s an important function because it helps keep you from becoming hypoglycemic and provides glucose to the few tissues that can’t use ketones.

However, gluconeogenesis can also ramp up during low-carb diets due to the lack of glucose in the diet. Since the body wants to hold onto energy (stored fat or glycogen in the liver), it can start breaking down muscle to turn into glucose for energy. Over time this can lead to muscle loss with increased amounts of glucose in the blood – which completely defeats the purpose of following a low-carb diet in the first place.

Gluconeogenesis and Insulin

A carb-rich diet turns off gluconeogenesis due to the presence of insulin. When insulin is present, gluconeogenesis is suppressed by 20%, and glycogenolysis (glucose made from glycogen) stops. Without carbs, insulin is unnecessary, so the body doesn’t release it.

Insulin is an anabolic hormone in the body, used for protein synthesis and facilitating glycogen storage. It’s essential for regulating blood sugar balance. Insulin is released by the pancreas when our blood sugar rises and sends a message to the cells to take the sugar out of our blood and into our cells for energy or fat storage. Insulin also controls gluconeogenesis not only in the liver but also in the muscles.

While excess insulin can lead to weight gain (and other health issues, as seen for people with insulin resistance), chronically low insulin levels from low-carb diets can change the body’s preferential fuel to muscle instead of fat.

It’s unclear why this happens to some people and not others, though some people appear to be more biologically predisposed. It may be that for those who experience muscle loss, the body prefers to store fat and spare stored glucose as an emergency energy source for fuel. This could be a biological adaptation left by our ancestors who needed to conserve quick energy if they encountered a predator or other dangerous situation.

In this situation, the body will break down muscle while hanging onto fat as a major energy source and glycogen in muscles and the liver if it needs fast, life-saving energy. The stored glucose is the quickest form of energy, so it makes sense it is smart enough to hold on to it. As a result, muscle mass shrinks and leaves belly fat behind. And as we age, this can become even worse as the body breaks down more muscle resulting in sarcopenia or loss of skeletal mass and function.

Keto and Muscle Loss: Cycling in and Out of Ketosis

Working with the body’s built-in survival mechanisms – instead of fighting against them – is the way we can combat this muscle loss from occurring. The body is designed to protect us; we should be thankful that it works this way. We can limit this problem if we support our body by reminding it that it has nutrients and will not starve.

One way to teach the body it is not starving it by cycling through periods of keto and fasting with set periods of increased nutrients (or “feasts”), especially carbohydrates, to slow down gluconeogenesis. This process not only spares muscle but also supports fat burning. It is a systematic, cyclical approach to help us support our skeletal muscles. And while increasing protein or calories can also help, carbohydrates tend to be the best at supporting this, likely through the release of insulin, which, as you learned, shuts down gluconeogenesis.

The key is not to overdo carbohydrate intake, which can backfire and lead to weight gain or fat storage. The amount and type of carbohydrates still matter, but giving the body what it needs will not feel like switching to survival mode. In this way, we can continue to reap the benefits of keto without the concern of muscle loss.

To sum it up – remember that all the body processes are designed to keep you healthy and safe. If we want to biohack our health through diet to give the body the extra push for long-term health, we need to find a way to support these systems instead of ignoring or fighting against them. Cycling in and out of keto with periods of fasting,  helps to accomplish this – so if you feel keto did not work for you, this may be the best place to start.